Your Genes Have a Social Life: How Social Contact Shapes Your Microbiome

We often consider our genetics to be deeply personal and individual. However, groundbreaking research published in Nature Communications demonstrates that our genes have a surprisingly social life.

The Social Life of Genes

After studying more than 4,000 rats under controlled conditions, scientists from the CRG of Barcelona and the University of California in San Diego discovered that an individual’s microbiome is largely determined by the genes of those they live with. This isn’t simply a matter of shared environment; it’s the result of genetic influences being transmitted through social contact. As Dr. Amelie Baud, a researcher at the Centre for Genomic Regulation (CRG) of Barcelona and the study’s lead author, explains, microbes move between individuals, carrying with them the effects of the genes that promote them.

Did You Know? Researchers studied over 4,000 rats to uncover the link between genetics and the microbiome.

Three Key Gene-Microbe Connections

The intestinal microbiome – the collection of trillions of microorganisms crucial for digestion and overall health – is known to be influenced by diet and medication. However, pinpointing genetic influences has proven more challenging. This research identified three key genetic regions that dictate which bacteria thrive in the gut.

St6galnac1: This gene adds sugars to intestinal mucus. The bacterium ‘Paraprevotella’ feeds on these sugars; the more sugar molecules the gene produces, the more abundant this bacterium becomes.
Mucin Genes: These genes, which compose the protective mucus layer, are linked to the bacterial group ‘Firmicutes’.
Pip: This gene produces an antibacterial molecule that regulates the presence of the Muribaculaceae family.

The Indirect Genetic Effect

Perhaps the most surprising finding is what researchers call the “indirect genetic effect.” They created a computational model to determine what portion of a rat’s microbiome was due to its own genes and what portion was attributable to the genes of its cage mates. The results showed that including social influence multiplied the weight of genetics on the microbiome by a factor of four to eight. This suggests that science has underestimated the role of genes in health by not accounting for the fact that a person’s genetic variants can alter the biology of those around them – without changing their DNA.

Expert Insight: This research highlights a previously unappreciated level of interconnectedness in biological systems, suggesting that health isn’t solely an individual matter but is also shaped by the genetic makeup of our social environment.

Dr. Baud emphasizes that these findings likely represent just “the tip of the iceberg,” with many more microbes potentially affected as analytical methods improve.

Implications for Human Health

If this mechanism is confirmed in humans, the implications for public health could be enormous. Researchers are already formulating hypotheses about common diseases. For example, the human equivalent of the St6galnac1 gene (ST6GAL1) has been linked to infections following vaccination. The bacterium Paraprevotella may degrade the enzymes the virus uses to enter cells, potentially offering extra protection if your genes – or those of your partner – favour this bacterium. They also hypothesize that alterations in Paraprevotella could be linked to IgA nephropathy, an autoimmune disease affecting the kidneys.

This discovery demonstrates that we share not only space and food, but also our genetics, which spread through social groups via the trillions of microorganisms we host, making health a collective phenomenon.

“I’m obsessed with this bacteria now,” concludes Dr. Braud. “Our results are supported and remarkably solid. It’s a unique opportunity.”

Frequently Asked Questions

What is the microbiome?

The microbiome is a collection of trillions of microorganisms that play key roles in digestion and overall health.

What is the “indirect genetic effect”?

The indirect genetic effect refers to the influence of an individual’s genes on the microbiome of those around them, even without directly altering the other individual’s DNA.

What role does the St6galnac1 gene play?

The St6galnac1 gene adds sugars to intestinal mucus, which then feeds the bacterium ‘Paraprevotella’.

Considering these findings, how might our understanding of public health strategies need to evolve to account for the interconnectedness of our genetic and microbial landscapes?